Constantes pré-definidas

As constantes abaixo estão sempre disponíveis como parte do núcleo do PHP.

Constantes matemáticas
Constante Valor Descrição Disponibilidade
M_PI 3.14159265358979323846 Pi  
M_E 2.7182818284590452354 e - número neperiano  
M_LOG2E 1.4426950408889634074 logaritmo de e na base 2  
M_LOG10E 0.43429448190325182765 logaritmo de e na base 10  
M_LN2 0.69314718055994530942 logaritmo neperiano de 2  
M_LN10 2.30258509299404568402 logaritmo neperiano de 10  
M_PI_2 1.57079632679489661923 pi/2  
M_PI_4 0.78539816339744830962 pi/4  
M_1_PI 0.31830988618379067154 1/pi  
M_2_PI 0.63661977236758134308 2/pi  
M_SQRTPI 1.77245385090551602729 raiz(pi)  
M_2_SQRTPI 1.12837916709551257390 2/raiz(pi)  
M_SQRT2 1.41421356237309504880 raiz(2)  
M_SQRT3 1.73205080756887729352 raiz(3)  
M_SQRT1_2 0.70710678118654752440 1/raiz(2)  
M_LNPI 1.14472988584940017414 logaritmo neperiano de pi  
M_EULER 0.57721566490153286061 Constante de Euler  
PHP_ROUND_HALF_UP 1 Arredonda 0.5 para cima  
PHP_ROUND_HALF_DOWN 2 Arredonte 0.5 para baixo  
PHP_ROUND_HALF_EVEN 3 Arredonda 0.5 para números pares  
PHP_ROUND_HALF_ODD 4 Arredonda 0.5 para números ímpares  
NAN NAN (como um float) Not A Number - um não-número  
INF INF (como um float) Infinito  

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User Contributed Notes 7 notes

md2perpe at gmail dot com
8 years ago
I just learnt of INF today and found out that it can be used in comparisons:

echo 5000 < INF ? 'yes' : 'no'; // outputs 'yes'
echo INF < INF ? 'yes' : 'no'; // outputs 'no'
echo INF <= INF ? 'yes' : 'no'; // outputs 'yes'
echo INF == INF ? 'yes' : 'no'; // outputs 'yes'

You can also take its negative:

echo -INF < -5000 ? 'yes' : 'no'; // outputs 'yes'

Division by INF is allowed:

echo 1/INF; // outputs '0'
Hayley Watson
11 years ago
There are also the predefined PHP_INT_MAX and PHP_INT_SIZE constants, that describe the range of possible integer values.
pemapmodder1970 at gmail dot com
7 years ago
Although INF can be used for comparison against normal numbers and as a directed number, and behaves as reciprocal of zero, it is not like limit INF tends to infinity. These operations do not work:

(INF / INF); // float(NAN)
var_dump(INF - INF); // float(NAN)

However, it works with arc-tangent:
(atan(INF) / M_PI); // float(0.5)
var_dump(atan2(INF, INF) / M_PI); // float(0.25)
var_dump(atan2(1, INF) / M_PI); // float(0)
Hayley Watson
6 years ago
From PHP 7.2.0, the PHP_FLOAT_* constants are provided to describe the properties of floating point numbers that can be stored; PHP_FLOAT_MAX, for example, is analogous to PHP_INT_MAX and represents the largest possible floating-point number.
br at ndon dot co
2 years ago
The constants


are constants intended to be used as the 3rd parameter in the math function round()
steve at websmithery dot co dot uk
6 years ago
Another observation on INF.

Division by zero results in INF:

(1/0); // float(INF)

BUT a 'Division by zero' warning is issued.
Kira-Bianca dot Hinz at web dot de
3 years ago
Caution when using variables with the value NAN (or directly NAN, which would not be logical) if the value is converted in any form (integer, string or other non-float format)!
In that case, NAN is converted to 0. (e.g. as an index in an array, argument of a method that takes it as a non-float parameter, etc.). This bug has been reported several times, but is still present in the current version PHP 7.3.15.

Example 1:
$array = [0 => 'zero', 1 => 'one', 2 => 'two'];
$index = NAN;
echo $array[$index]; // echo 'zero' and not as axcepted throws an exception or at least a warning 'undefined offset NAN ...'

Example 2:
function f((int) $p) { return $p; }
echo f(NAN); // echo 0 because the argument (NAN) has been converted to integer (0)

It would have to be checked in both cases explicitly for is_nan():
1: if(is_nan($index)){
<throw Exception>
echo $array[$index];

2: function f($p){ // without converting!!!
<throw Exception>
return (int)$p; // actually a correct conversion to Integer would have to be checked because the parser does not check this here.
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